Gas-fractionating device



July 16, 1957 c. o. JoNKr-:Rs l-:TAL 2,799,141

GAsv-FRAcTroNATmG DEVICE:

3 Sheets-Sheet 1 Filed Oct. 5, 1954 Inl rrV/VV//Vh/////////// ENTOR J uns.

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GAS-FRACTIONATING' DEVICE Filed oct. s, 1954 s sheets-sheet s JONKEBS To JAcoawlLLEM LAURENsKol-ud BY ZZ( u 35,9. nndnn 1 y u H1 9 w1 eaera l a United States Patent O GAS-FRACTIONATING DEVICE Corneiius Otto Jonkers and Jacob Willem Laurens Khler,

Eindhoven, Netherlands, assignors, by mesne assignments, to North American Philips Company, Inc., New York, N. Y., a corporation of Delaware Application October 5, 1954, Serial No. 460,362

Claims priority, application Netherlands October 9, 1953v Claims. (Cl. 62-2) The invention relates to a gas-fractionating device comprising a gas-fraetionating column from which heat is withdrawn by means of a gas refrigerator. The term gas refrigerator as used herein means a refrigerator working on Vthe reversed hot-gas reciprocating engine principles. As is well known, such engines may be realised in various manners,rfor example, as displacer engine, as double-acting engine, as engine the cylinders of which are arranged in the form of a V or as an engine the working space of which is combined with that of the ho-gas reciprocating engine.

In gas-fractionating columns it will generally be desirable for a control arrangement to be provided which ensures that during operation and especially on variation of the production, the level of the liquid in the boiling vessel of the column is maintained substantially constant. For this purpose in the known gas-fractionating devices provision is usually made of one or more cocks which enable the quantity of the washing liquid flowing down in the column to be varied. Consequently in the known devices continuous supervision is desired.

It has already been proposed to realise a gas-fractionating device such that vapour is drawn olf from the column and condensed by means of a gas refrigerator after which at least part of the condensation product is supplied to the column by means of a vapour-bubble pump effect at a point situated above the outlet `for this condensate from the gas refrigerator. Since the height of the gas-fractionating column generally will exceed that of the gas refrigerator, without special expedients the point of the gas refrigerator at which the condensate is drawn olf will have to be situated above the point at which the condensate is supplied to the column. In many cases thiswill be undesirable for structural reasons. If in contradistinction thereto use is made of a vapour-bubble pump effect, the gas fractionating column and the gas refrigerator may be arranged on the same foundation or at least so that the height of the point of the columnat which the gas refrigerator after which at least part of the condensate is supplied to the column by means of a vapourbubble pump effect at a point situated above the outletl ofy this condensate from the gas refrigerator, the quantity of condensate displaced by means of a vapour-bubble pump effect is governed by the level of the liquidinthe boiling vessel of the column, any remainder of the condensate being drawn off from the refrigerator. Thus, a

rise of the level of theliquid in the boiling vessel will have to involvea reduction of the quantity of condensatef 2 supplied to the column, whilst a fall of the level willv have to involve an increase of the quantity displaced.

The above-described device can be used successfully if the fraction having the lowest boiling point which v escapes from the column is condensed by the gas refrigerator, whilst part of the produced condensate is supplied. by means of a vapour-bubble pump effect to the column and the remainder is drawn olf from the gas refrigerator.

lf in contradistinction thereto heat is withdrawn from the gas-fractionating column by means of an intermediate medium, whilst this intermediate medium is evaporated in a condenser accommodated in the column and the vapour produced is condensed by the gas refrigerator, use may be made of a different construction. In an alternative embodiment of a gas-fractionating device according to the invention the'column in this case comprises more than one condenser to each of which part of the produced condensate is supplied by means of a vapourbubble pump effect, whilst the quantity of condensates supplied to each of these condensers is governed by the level of the liquid in the boiling vessel. In such a device the product obtained, for example, the fraction having the lowest boiling point, will usually be drawn ofIr Afrom the column, In this event one of the condensers can be substantially utilised to condense the washing liquid, and the other to condensate that part which can be drawn off as obtained product. The ratio between the quantity of washing liquid produced and the quantity of product obtained can be varied by varying the vapourbubble pump effect in one or more of the supply pipes supplying one of the condensers. If air is separated into fractions, use may, for example, be made of nitrogen as the intermediate medium.4

ln a further embodiment of a gas-fractionating device u according to the invention, in which the fraction having the lowest boiling point is condensed by a gas refrigerator,

part of the condensate is supplied to the column by means of a vapour-bubble pump effect, whilst another part of the condensate is drawn oif from the device by means of a vapour-bubble pump effect also and the quantity thereof is governed by the level of the liquid in the boiling vessel.

If the condensate is conveyed to the column by means of more `than one vapour-bubble pump, the vapourbubble pump effect can be increased or reduced by switching on or switching off one or more of these vapourbubble pumps. However, a simple construction is obtained if according to a further embodiment of the invention the quantity of heat supplied to the liquid required to be displaced by means of the vapour-bubble pump effect is governed by the level of the liquid in the boiling vessel of the column. Consequently this embodiment enables the effect of the vapour-bubble pump itself to'be varied. Y

The required quantity of heat may be supplied in various manners, for example, by means of an electric heating spiral. The quantity of heat supplied by the spiral can in this event be governed by the level of the liquid in the boiling vessel.

In a further embodiment of a gas fractionating device according to the invention the heat is supplied by means of a member made of a material having `a coeicient of thermal conduction of at least 0.1 cal./cm. sec. C., part of which is at a higher temperature `than the condensate whilst'means are yprovided to vary the temperature of this part. The'metalvmember may, for example, be designed as a copper rod one end of which is secured to the pipe through which the condensate required to be displaced passes, whilstthe other end is maintained at a temperature exceeding thatof the condensate, with the result that through this rodpheat can be supplied, to the condensate. J

The quantity of the heat supplied to the condensate by means of this rod can be varied in various manners. In one embodiment of the device according to the invention the liquid in the boiling vessel is in heat-exchanging contact with the metal member. if in this embodiment the level of the liquid in the boiling vessel rises, the rod will be covered by the liquid to a greater or less extent with the result that a greater or lesser quantity of heat is supplied to the condensate.

In a further embodiment of a device according to the invention the gas required to be separated is precooletl in a heat exchanger arranged outside of the boiling vessel, whilst the member is in heat-exchanging contact with this heat exchanger -at a point at which a temperature prevails exceeding that prevailing in the boiling vessel, whilst at the same time at a point of the body situated between the heat exchanger and the vapour-bubble pump the liquid in the boiling vessel may be in heat-exchanging contact with this member.

In a further embodiment of the device according to the invention the boiling vessel comprises an overow such that if the level of the liquid in the boiling vessel rises, a greater quantity of liquid is in heat-exchanging contact with the member.

The invention will now be explained with reference to the accompanying drawing, in which some embodiments of a device according to the invention are shown by way of example, and in which Figs. l and 2 show a gas-fractionating device in which by means of a metal member an additional quantity of heat is supplied to a part of the condensate required to be displaced, the metal member at one end being in heat cxchanging contact with the heat exchanger in which the gas mixture required to be fractionated is pre-cooled. Fig. 2 is a cross-sectional view taken along the line vlI---Il of Fig. 1.

Figs. 3 and 4 show an embodiment in which the metal member is in heat-exchanging contact with the medium contained in the boiling vessel of the gas-fractionating column, whilst the quantity of medium drawn olf from the device is governed by the heat supplied by this member. Fig. 4 is a cross-sectional view taken along the line IV-lV of Fig. 3.

Figs. 5 and 6 show a device in which heat is withdrawn from a gas-fractionating column by means of an intermediate medium. Fig. 6 is a cross-sectional view taken along the line VI-VI of Fig. 5.

Referring now to Figs. 1 and 2, the gas-fractionating device comprises a gas-fractionating column 1 comprising a boiling vessel 2. After impurities have been removed from thc gas mixture required to be fractionated this mixture is supplied through a pipe 3 to a heat exchanger 4. This heat exchanger is connected to the bottom 6 of the boiling vessel 2 by means of a tubular support 5 so that part of the heat withdrawn from the gas mixture required to be fractionated is supplied via the support and the bottom, which comprises vanes 7, to the liquid contained in the boiling vessel so that this liquid evaporates. The cooled gas mixture flows through an annular duct 8 surrounding the boiling vessel 2 and the column 1 and enters the column through apertures 9. In the column the gas mixture is separated into fractions. The liquid part of the fraction having the highest boiling point flows down in the column and is collected in the boiling vessel.

The column is separated from the boiling vessel by a partition 10. This partition comprises a pipe 11 and an aperture 12 having a smaller passage. The Vfraction having the highest boiling point flows through the pipe 11 into the boiling vessel; however, part of the vapour produced in the boiling vessel again rises in the column through the aperture 12. The resistance of the aperture 12 is arranged such that the pressure prevailing in the boiling vessel exceeds the atmospheric pressure. This enables part of the vapour produced in the boiling vessel to be drawn olic therefrom via a pipe 13 and vthe heat;`

exchanger 4. The vapour llows through the support S, which comprises internal and external vanes, and thus is in heat-exchanging contact with the gas mixture required to be fractionated and subsequently is discharged from the device through a pipe 14.

The fraction having the lowest boiling point which is available at the upper end of the column is supplied to a gas refrigerator 17 via a pipe 15 and a pipe 16. In the gas refrigerator the vapour is condensed. The refrigerator is driven by an electric motor 18. The condensate produced is conveyed to an annular duct 2t) surrounding the column via the pipe 16 and a pipe 19.

As is shown in Fig. 2 also, the annular duct 20 has three vertical pipes 21, 22 and 23 connected to it. These pipes are secured to the outer wall of the duct 8. Through this duct 8 the gas mixture required to be fractionated ows, whilst the pipes 21, 22 and 23 contain the condensate of the fraction having the lowest boiling point. Due to the temperature difference between the two media a vapour-bubble pump effect is set up in this condensate so that it is pumped upwards.

Consequently the condensate rises in the pipes 21, 22 and 23. The pipes 21 and 22 open into the column, whilst the pipe v23 drains off the condensate from the device. For this purpose the pipe 23 is connected with one portion of a pipe 24 comprising a liquid trap 25. The lengths of the pipe portion 24 is such that due to the partial vacuum (pressure below atmospheric) produced thereby the gas mixture required to be fractionated is sucked in by the pipe 3, the heat exchanger 4 and the column. The pipes 21 and 22 by means of a metal strip 26 are in heatexchanging contact with a member 27 made of a material of yhigh thermal conductivity, for example copper. This metal member. 27 is connected to the heat exchanger 4 in a heat-conducting Vmanner so that at this end a lemperature prevails considerably exceeding the temperature of the condensate. The. boiling vessel 2 comprises an overflow 28 communicating with a space 29 surrounding the body 27 at a vpoint between the hot and cold ends thereof. At this point the member comprises vanes 30.

The device operates as follows: The absorbed gas mixture for example air, is purified from water vapour and carbon vdioxide and subsequently flows via the pipe 3, the heat exchanger 4 and the annular duct 8 to the column, in which it is separated into fractions. The fraction having the highest boiling point, in this case the oxygen, is connected in the boiling vessel 2, whilst the nitrogen escapes at the upper end of the column and is condensed by the gas refrigerator 17.

The condensate is supplied to the pipes 21, 22 and 23 via the pipe 19 and the annular duct 20. By means of the air owing through the annular duct 8 and by means of the metal member 27 heat is supplied to the condensate in the pipes 2'1 and 22. If the quantity of washing liquid supplied to the column is excessive, the level of the liquid in the boiling vessel rises and consequently the liquid flows over the overflow into the space 29 with the result that the rod 27 is cooled and consequently less heat is supplied to the pipes 21 and 22. Naturally it is of importance for the space 29 to be spaced away from the hot end ofthe rod 27 by a distance such that the temperature at 'this point due to the fall of temperature through rod exceeds the temperature of the liquid contained in the boiling vessel.

Figs. 3 and 4 show-an embodiment of a device accordingto the invention on -a different scale. In these figures like parts are designated-by like reference numbers as in the device shonw in Figs. 1 and 2.

After removal of the impurities the gas mixture required to be fractionated is supplied through the pipe 3 andthen flows through the heat exchanger 4 and the annular duct 8 to the column 1 similarly to what has been described with reference to the device shown in Fig. l. The fraction having the highest boiling point is collected in the. boiling vessel 2 and evaporates therein. The fraction having the lowest boiling point is condensed'by va gas refrigerator (not shown) and the condensate is drawn off from the gas refrigerator through the pipe 19. Similarly to Fig. 1, this pipe is connected to an annular duct 20 comprising three pipes 21, 22 and 23 in which a vapourbubble pump eiect is maintained. The pipe 23 draws olif condensate from the device, whilst the pipes 21 and 22 supply the condensate as washing liquid to the column. The boiling vessel comprises an overflow 28 leading to a space 29. In this space 29 provision is made Vof a metal member 40 which, similarly to the member 27 shown in Fig. l, is in heat-exchanging contact with the pipe 23 through which the condensate is drawn off from the device. Y

The device operates as follows: If the level of the liquid in the boiling vessel is low, there is no liquid in the space 29, so that, no or substantially no heat is supplied via the metal member 4t) to the pipe 23 and consequently the vapour-bubble pump effect in the pipe 23 is not stimulated. The device is constructed such that in this event a comparatively large quantity of liquid is supplied to the column through the pipes 21 and 22 with the result that the level of the liquid in the boiling Vessel 2 rises. This process continues until the liquid Hows into the space 29 via the overflow 28. As a result heat is supplied to the metal member 40. This heat is supplied via the metal member 40 to the pipe 23. Consequently the vapour-bubble pump effect in this pipe is stimulated, so that a larger quantity of condensate is drained off from the device and consequently a lesser quantity of condensate is supplied to the column. The higher the level of the liquid in the space 29 rises, the greater amount of liquid is drained off from the column and the lesser amount of liquid enters the column. 'Ihe member 40 is made of a material of high thermal conductivity having a coefficient of thermal conductivity exceeding 0.1 caL/cm. sec. C., for example copper.

In the device shown in Figs. and 6 heat is withdrawn from the column via a heat transference intermediate medium. In the device shown in these figures also, parts corresponding to those shown in Figs. 1 and 2 are designated correspondingly.

At its upper end the device comprises two condensers 50 and 51 to which a heat transference intermediate medium, for example nitrogen, can be supplied. The nitrogen vaporises, so that heat is withdrawn from the column and the vapour is fed through pipes 52 and 53 and the pipe 54 to the gas refrigerator 17, in which it is condensed. The condensate is supplied through a pipe 55 to an annular pipe 56 surrounding the column 1. To this annular pipe four vertical pipes 57, 58, 59 and 60 are connected in which a vapour-bubble pump effect is maintained. The pipes 57 and 58 are connected to the condenser 50 and the pipes 59 and 60 to the condenser 51. To the pipes heat is supplied by means of the gas mixture required to be fractionated which passes through the annular duct 8. However, the pipes 57 and 58 are also connected via a metal strip 61 in a heat conducting manner to the metal member 27 by means of which heat may be supplied to the pipes in a manner similar to that described with reference to Fig. l.

Between the condensers 50 and 51 provision is made of an annular duct 62 in which the medium condensed by the condenser 51 can be largely collected after which it can be drawn off from the device through a pipe 63.

This device operates as follows: the gas mixture required to be fractionated, for example air, is supplied to the column via the pipe 3, the heat exchanger 4 and the annular duct 8. The liquid part of the fraction having the highest boiling point, for example oxygen, is collected in the boiling vessel, in which it evaporates again, as has been described above with reference to Figs. l and 2. The vaporous part of the fraction having the lowest boiling point is condensed in the condensers 50 and 51 accommodated in the upper end of the column. In accordance `6 with the quantity of heat withdrawnby each of the condensers a greater or lesser quantity of vapour is produced by each of the condensers. If much heat is withdrawn from the vapour by the condenser 53, a large quantity of condensate is collected in the annular duct 62 and drawn off from the device with the result that the quantity of washing liquid flowing back in the column is slight. However, if much heat is withdrawn from the condenser 50, the quantity of washing liquid is large. The quantity of heat withdrawn from the condensers is governed bythe quantity of liquid raised by the pipes 57, 58 and S9, 60 respectively. If the quantity of liquid in the boiling vessel is small, so that no liquid ows into the space 29 via .the

. overflow 28, similarly what has been described with reference to Fig. l, much heat is supplied to the pipes 57 and 58 with the result that a large quantity of liquid is raised to the condenser 50. Consequently the quantity of heat withdrawn from the condenser 51 is small and that withdrawn from the condenser 50 is large with the result thaty a small quantity vof condensate is drawn oi from the device and a large quantity flows back as Washing liquid. Consequently the level of the liquid in the boiling vessel rises. At a certain instant liquid flows via the overflow 28 into the space 29 with the result that, similarly to what has been described with reference to Fig. l, a smallerquantity of heat is supplied to the pipes 57 and 58 and consequently liquid is supplied to the condenser 51 and a larger quantity of heat is withdrawn therefrom, with the result that a larger quantity of liquid is again drained off from the device. Thus, a state of equilibrium of the level of the liquid is automatically produced.

In the above-described embodiments by means of a metal member heat is supplied to the pipes in which a vapour-bubble pump effect has to be maintained. However, it is also possible to supply heat to these pipes by means of an electric heating spiral. In this event the quantity of heat thus supplied has to be governed in accordance with the level of the liquid in the boiling vessel. However, in most cases the embodiments described will be preferable by reason of their simplicity.

What is claimed is:

l. A gas-fractionating device comprising a gas-fractionating column provided with a boiling vessel, a cold-gas 'refrigerator for withdrawing heat from said column includmg outlet means, means for drawing olif vapor fromv said column, said vapor being condensed by said cold-gas refrigerator, means for creating a vapor lift pump effect whereby at least part o-f the condensate is supplied to the column at a point situated above said outlet of the coldgas refrigerator, and means `associated with the liquid level in the boiling vessel of said column for controlling the quantity of condensate supplied to said column while the remainder of said condensate is drained off from said cold-gas refrigerator.

2. A gas-fractionating Idevice as set forth in claim l wherein said cold-gas refrigerator condenses the fraction having the lowest boiling point and part of said condensation product being supplied to said column by means of said vapor lift pump effect, the remainder of said condensation product being `drawn off from said cold-gas refrigerator.

3. A gaS-fractionating device as set forth in claim l further comprising at least two condensers in said column wherein part of said condensate produced by said cold-gas refrigerator is supplied by means of said vapor lift pump effect to each of said condensers, the quantity of condensate supplied to each of said condensers being controlled by the level of the liquid in said boiling vessel.

4. A gas-fra-ctionating device as set forth in claim 2 wherein the quantity of condensation product drawn off from said cold-gas refrigerator is controlled by the liquid level in said boiling vessel.

5. A gas-fractionating device as set forth in claim l wherein a quantity of heat is supplied to the liquid in said column required to be displaced by means of said vapor lift pumpveffect, said quantity of-heat being'governed by the liquid level in the boiling vessel of said'column.

6. A gas-fractionating device as set forth in c-laim 5 wherein the quantity of heat required in order toproduce said vapor lift pump effect is supplied by conduction.

7. A gas-fractionating device as set forth in claim 5 further comprising an element for supplying heat to said liquid, said element constituted of material having a coeicient of thermal conductivity of at least 0.1 cal/cm. sec.- C part of said element having a temperature-exceed-ing that of said condensate,fand means for varying the temperature of said part.

8. A gas-fractionating device as set forth in claim 7 wherein said element is metal and the liquid in said boiling vessel is in heat-exchanging relationship therewith.

9. A gas-fractionating device as set forth in claim 7 further comprising a pre-cooling heat exchanger positioned outside said boiling vessel, said elementfbeing in heat exchanging contact with said heat exchanger yat `a point at which a temperature prevails which exceeds the 20 prevailing temperature in saidboiling vessel, said element alsoy being in heat-exchanging contact with` the liquid in said'boiling vessel.

10. A gas-fractionating device vas set forth in claim 8 wherein said boiling vessel comprises an `overflow so that when the level of the liquid in the boiling vessel rises to a predetermined level a quantity of liquid is in heatexchanging'contact withisaid element.

References `Cited in the file of this patent UNITED STATES PATENTS 1,512,268 Barbet Oct. 2l, 1924 1,594,336 Mewes July 27, 1926 2,142,446 Kopp Jan. 3, 1939 2,650,482 Lobo Sept. 1, 1953 FOREIGN PATENTS 240,412 Great Britain ian. 2l, 1926 587,688 France Apr. 22, 1925 

1. A GAS-FRACTIONATING DEVICE COMPRISING A GAS-FRACTIONATING COLUMN PROVIDED WITH A BOILING VESSEL, A COLD-GAS REFRIGERATOR FOR WITHDRAWING HEAT FROM SAID COLUMN INCLUDING OUTLET MEANS, MEANS FOR DRAWING OFF VAPOR FROM SAID COLUMN, SAID VAPOR BEING CONDENSED BY SAID COLD-GAS REFRIGERATOR, MEANS FOR CREATING A VAPOR LIFT PUMP EFFECT WHEREBY AT LEAST PART OF THE CONDENSATE IS SUPPLIED TO THE COLUMN AT A POINT SITUATED ABOVE SAID OUTLET OF THE COLD- 